Rybakina, playing her first match since her win over Ons Jabeur in the final of the grasscourt major, lost 1-6 6-2 6-0 to Daria Kasatkina. Seventh seed Rybakina looked to be in control early on but lost 12 of the last 14 games of the match.
"I was playing well in the first set and then conditions changed a bit and I think physically, I completely lost focus in the end," Rybakina said.
"Of course it was a tough week after Wimbledon. I had many things to do, I had a lot of travelling. I didn't have enough time to prepare for the hard season.
"I just wanted to come here and try my best because I knew I was coming to a very tough tournament. Here there are so many great players and I knew I could play in the first round with someone in the top 10."
Rybakina will be looking to bounce back in the WTA 1000 tournament in Toronto on August 8th, with eyes firmly on the final Grand Slam of the year, the US Open.
Follow the rest of the WTA San Jose results at Flashscore.
